The present invention relates to a fuser member and method for fusing toner images in an electrostatographic reproducing apparatus. The present invention further relates to a method for preparation of such a fuser member. More specifically, the present invention relates to methods and apparatuses directed towards fusing toner images using a fuser member having an amino silane adhesive layer and an outer fluoroelastomer layer, and methods for the preparation of such fuser members.
In a typical electrostatographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles which are commonly referred to as toner. The visible toner image is then in a loose powdered form and can be easily disturbed or destroyed. The toner image is usually fixed or fused upon a support which may be the photosensitive member itself or other support sheet such as plain paper.
The use of thermal energy for fixing toner images onto a support member is well known. To fuse electroscopic toner material onto a support surface permanently by heat, it is usually necessary to elevate the temperature of the toner material to a point at which the constituents of the toner material coalesce and become tacky. This heating causes the toner to flow to some extent into the fibers or pores of the support member. Thereafter, as the toner material cools, solidification of the toner material causes the toner material to be firmly bonded to the support.
Typically, the thermoplastic resin particles are fused to the substrate by heating to a temperature of between about 90xc2x0 C. to about 200xc2x0 C. or higher depending upon the softening range of the particular resin used in the toner. It is undesirable, however, to increase the temperature of the substrate substantially higher than about 250xc2x0 C. because of the tendency of the substrate to discolor or convert into fire at such elevated temperatures, particularly when the substrate is paper.
Several approaches to thermal fusing of electroscopic toner images have been described. These methods include providing the application of heat and pressure substantially concurrently by various means, a roll pair maintained in pressure contact, a belt member in pressure contact with a roll, a belt member in pressure contact with a heater, and the like. Heat may be applied by heating one or both of the rolls, plate members, or belt members. The fusing of the toner particles takes place when the proper combination of heat, pressure and contact time are provided. The balancing of these parameters to enable the fusing of the toner particles is well known in the art, and can be adjusted to suit particular machines or process conditions.
It is important in the fusing process that minimal or no offset of the toner particles from the support to the fuser member take place during normal operations. Toner particles offset onto the fuser member may subsequently transfer to other parts of the machine or onto the support in subsequent copying cycles, thus increasing the background or interfering with the material being copied there. The referred to xe2x80x9chot offsetxe2x80x9d occurs when the temperature of the toner is increased to a point where the toner particles liquefy and a splitting of the molten toner takes place during the fusing operation with a portion remaining on the fuser member. The hot offset temperature or degradation of the hot offset temperature is a measure of the release property of the fuser, and accordingly it is desired to provide a fusing surface which has a low surface energy to provide the necessary release. To ensure and maintain good release properties of the fuser, it has become customary to apply release agents to the fuser roll during the fusing operation. Typically, these materials are applied as thin films of, for example, silicone oils to prevent toner offset.
The process for the preparation of such fuser members is important in maintaining desired fuser life. Further, the composition of the layers, including the adhesive layer, are important in providing sufficient fuser life and prevention of toner offset. In particular, the bond between the fuser substrate and the outer surface must be sufficient in order to prevent the outer surface of the fuser member from debonding, resulting in fuser failure. The bond between the surface of the fuser member and the outer layer degrades as a function of time at the elevated temperatures involved in the fusing process which may exceed 400xc2x0 F. Known adhesives such as the THIXON(copyright) epoxy adhesive (THIXON(copyright) is a trademark of Dayton Chemical Products Laboratories) degrade to the point where they no longer function as an adhesive and failure is experienced with wholescale debonding of the fusing layer from the fuser substrate, such that the fusing surface may be manually peeled from the substrate.
Known epoxy adhesives further require baking for solidification. This baking step is an additional timely and costly step in the manufacture of fuser members.
It is also important that the adhesive react sufficiently with the substrate and the outer layer so as to provide an even coat and to provide sufficient bonding of the outer layer. Known adhesives have been shown to form clumps and uneven coating of the fuser substrate.
Another important feature of the adhesive is that it should be compatible for use with processes for preparing fuser rolls. Known processes for providing surfaces of fuser members include two typical methods which are dipping of the substrate into a bath of coating solution or spraying the periphery of the substrate with the coating material. However, recently, a process has been developed which involves dripping material spirally over a horizontally rotating cylinder. Generally, in this new flow coating method, the coating is applied to the substrate by rotating the substrate in a horizontal position about a longitudinal axis and applying the coating from an applicator to the substrate in a spiral pattern in a controlled amount so that substantially all the coating that exits the applicator adheres to the substrate. For specific details of an embodiment of the flow coating method, attention is directed to commonly assigned, U.S. application Ser. No. 08/672,493 filed Jun. 26, 1996, entitled, xe2x80x9cFLOW COATING PROCESS FOR MANUFACTURE OF POLYMERIC PRINTER ROLL AND BELT COMPONENTS,xe2x80x9d the disclosure of which is hereby incorporated by reference in its entirety.
However, not all coatings and adhesives are compatible with the new flow coating method. Specifically, only materials which can be completely dissolved in a solvent can be flow coated. Further, it is desirable that the coating material have the ability to remain dissolved during the entire flow coating process which may take up to approximately 8 hours or longer, and remain dissolved during the manufacturing period which may take up to several days, for example about 1 to 5 days. Satisfactory results are not obtained with materials which tend to coagulate or crystallize within the time period required for flow coating. It is desirable to use a material capable of being flow coated for an increased amount of time to enable flow coating in a manufacturing and production environment. It is very costly to periodically shut down a manufacturing line and change the solution delivery system. If the adhesive does not have the desired properties, the assembly line may need to be shut down often, for example, every hour or every few hours in order to clean the delivery line of coagulated or crystallized material. Therefore, it is desirable to use a material which has good flow coating properties in order to allow for manufacturing to continue for a long period of time, for example several days, without occurring the above problems in the procedure.
It is also desirable that the adhesive be slow drying to avoid trapping solvent in the under layers which tends to cause bubbles and solvent xe2x80x9cpops.xe2x80x9d Bubbles result from trapped air in the coating which results in non-uniformity of coating and or surface defects. Solvent xe2x80x9cpopsxe2x80x9d are defined as trapped air or solvent voids that rupture resulting in crater-like structures causing non-uniform coated areas or surface defects. In either case, these defects can act as initiation sites for adhesion failures.
In addition, good results are not obtained with materials which are not reactive with solvent coatings.
Moreover, useful materials for the flow coating process should possess the ability to flow in a manner which allows for the entire roll to be coated. Therefore, it is desirable that the material possess a desired viscosity which allows it to flow over the entire surface of the member being coated. Along with these properties, it is desirable that the material to be coated possess a balance between viscosity and percent solids to enable sufficient build rates which impact throughput and work in process. Build rates are defined as the thickness of a material that can be coated per unit time. The thickness of the material should allow for a balance between maintaining thickness uniformity and avoiding solvent xe2x80x9cpopsxe2x80x9d and air bubbles. Throughput in the process is the number of units that are processed per unit time. Work in process (WIP) is the number of units currently in any one of the process stages from beginning to end. The objective is to maximize the build rate and reduce the throughput time and work in process.
Also, although not a necessary feature of materials useful in the flow coating procedure, it is desirable that the material not require baking for solidification. The baking step is costly and time consuming. The elimination of the baking step provides a time savings for the manufacture and a cost savings to the customer.
Many materials known to be useful for outer coatings of a fuser member, such as, for example, fluoroelastomers, possess the above qualities necessary for flow coating. However, most known adhesives do not possess the above qualities and many problems are associated with the flow coating of adhesives.
Particularly, well-known adhesives such as epoxy resins and the like cannot be flow coated because epoxy resins do not possess many of the above qualities. In addition, epoxy resins require baking before coating an outer layer thereon. Similarly, many known amino silane adhesives have a short pot life and a reduced life. Therefore, such adhesives cannot be successfully flow coated.
U.S. Pat. No. 5,332,641 to Finn et al., the disclosure of which is hereby incorporated by reference in its entirety, discloses a fuser member having an amino silane cured fluoroelastomer adhesive layer and thereon, an outer elastomer fusing surface.
U.S. Pat. No. 5,049,444 to Bingham et al., the disclosure of which is hereby incorporated by reference in its entirety, discloses a multilayered fuser member having in sequential order a base support member, an adhesive layer comprising a fluoropolymer and a silane coupling agent, a tie coat layer, and an outer elastomeric layer comprising a metal oxide filled fluoropolymer.
U.S. Pat. No. 5,219,612 to Bingham et al., the disclosure of which is hereby incorporated by reference in its entirety, teaches a method of using a multilayered fuser member having in sequential order a base support member, an adhesive layer comprising a fluoropolymer and a silane coupling agent, a tie coat layer, and an outer elastomeric fusing surface.
There exists a need for an adhesive which provides adequate bonding of the outer layer to the fuser member substrate, reacts sufficiently with the outer layer to provide even coating of the outer layer, and can be used with new flow coating procedures of preparation of fuser members. The qualities necessary for sufficient flow coating include providing slow solidification following flow coating, possessing the ability to substantially dissolve in a solvent and remain dissolved throughout the flow coating and manufacturing procedures, being non-reactive with solvents, and providing a sufficient balance between flowability, viscosity and percentage solids.
Examples of objects of the present invention include:
It is an object of the present invention to provide methods and apparatuses with many of the advantages indicated herein.
It is another object of the present invention to provide an adhesive which sufficiently bonds the outer surface of a fuser member to the fuser member substrate.
A further object of the present invention is to provide an adhesive which coats evenly when coated on a fuser substrate.
Another object of the present invention is to provide an adhesive which is able to be coated over an increased period of time in a production and/or manufacturing environment without crystallizing or coagulating.
It is yet another object of the present invention to provide an adhesive which is slow drying following coating thereof.
Further, an object of the present invention is to provide an adhesive which has the ability to substantially dissolve in a solvent.
Yet another object of the present invention is to provide an adhesive which has the ability to be sufficiently viscous when mixed with a solvent.
Still yet another object of the present invention is to provide an adhesive which is non-reactive with most solvents.
A further object of the present invention is to provide an adhesive which aids in providing improved fuser life.
Another object of the present invention is to provide an adhesive which does not require baking for solidification.
In embodiments, the present invention relates to a fuser member comprising: a) a substrate; and thereover b) an amino silane adhesive coating comprising an amino silane composition and an organic phosphonium catalyst; and having thereon, c) a fluoroelastomer outer coating comprising a fluoroelastomer.
Embodiments of the present invention further include: a process for the preparation of a fuser member comprising in sequential order a substrate, an amino silane adhesive coating comprising an amino silane composition and an organic phosphonium catalyst, and an outer fluoroelastomer coating comprising a fluoroelastomer, the process comprising: a) providing a substrate; b) rotating the substrate in a horizontal position about a longitudinal axis thereof; and simultaneously c) applying at least one of an amino silane adhesive coating and an outer fluoroelastomer coating in solution form by rotating the substrate in a horizontal position about a longitudinal axis thereof and simultaneously applying the solution coating from an applicator to the substrate in a spiral pattern in a controlled amount so that substantially all the coating from the applicator adheres to the substrate.
Embodiments of the present invention further include: an image forming apparatus for forming images on a recording medium comprising: a charge-retentive surface to receive an electrostatic latent image thereon; a development component to apply toner to the charge-retentive surface to develop the electrostatic latent image to form a developed image on the charge retentive surface; a transfer component to transfer the developed image from the charge retentive surface to a copy substrate; and a fuser member for fusing toner images to a surface of the copy substrate, wherein the fuser member comprises: a) a substrate; and thereover b) an amino silane adhesive coating comprising an amino silane composition and an organo phosphonium catalyst, and having thereon, c) a fluoroelastomer outer coating comprising a fluoroelastomer.